1. Field of the Invention
The present invention relates to an arteriosclerosis evaluating apparatus which evaluates arteriosclerosis of a living subject based on afterload acting on the subject's heart.
2. Related Art Statement
Pulse-wave propagation velocity or pulse-wave augmentation index is known as an index used to evaluate arteriosclerosis of a living person. Pulse-wave propagation velocity is a velocity at which a pulse wave propagates between two portions of a person, and it increases as the person's arteriosclerosis advances. Pulse-wave augmentation index, known as AI, is generally determined as a percentage of a value obtained by dividing a magnitude difference between a magnitude of a pulse wave at the time of occurrence of a reflected-wave component of the pulse wave and a magnitude of a peak point of an incident-wave component of the pulse wave, by a pulse pressure of the pulse wave, and there is a tendency that this index increases as arteriosclerosis advances.
In addition, cardiac afterload, i.e., afterload acting on person's heart changes in relation with arteriosclerosis. The cardiac afterload is known as a load that is exerted to the heart by the resistance of peripheral blood vessels, such as aorta and arterioles. The reason why cardiac afterload relates to arteriosclerosis is that the harder the arteries are, the greater the resistance of the blood vessels is and accordingly the harder the arteries are, the greater the load acting on the heart at the time of ejecting blood is.
Cardiac afterload provides different information about evaluation of arteriosclerosis, than the information provided by the conventional arteriosclerosis-evaluation indexes such as pulse-wave propagation velocity or pulse-wave augmentation index. Thus, it is expected that if cardiac afterload is used either solely or in combination with one or more conventional arteriosclerosis-evaluation indexes such as pulse-wave propagation velocity or pulse-wave augmentation index, arteriosclerosis can be evaluated with higher accuracy.
However, as described above, cardiac afterload is a load exerted to person's heart by resistance of peripheral blood vessels, and accordingly it is difficult to directly measure it. Thus, there has not been practiced to measure cardiac afterload and evaluate arteriosclerosis based on the measured afterload.